Skin and nasal colonization of coagulase-negative staphylococci are associated with atopic dermatitis among South African toddlers

Background Skin colonization with coagulase-negative staphylococci (CoNS) is generally beneficial, but recent investigations suggest its association with flares and atopic dermatitis (AD) severity. However, this relationship remains unclear. Objective To assess patterns of staphylococcal colonization and biofilm formation in toddlers with and without AD from rural and urban South African settings. Methods We conducted a cross-sectional study of AD-affected and non-atopic AmaXhosa toddlers from rural Umtata and urban Cape Town, South Africa. CoNS isolates were recovered from lesional, nonlesional skin samples and the anterior nares of participants. Identification of the staphylococci was achieved by MALDI-TOF mass spectrometry. The microtiter plate assay assessed in-vitro biofilm formation. Results CoNS and S. aureus commonly co-colonized nonlesional skin among cases (urban: 24% vs. 3%, p = 0.037 and rural 21% vs. 6%, p<0.001), and anterior nares in urban cases (24% vs. 0%, p = 0.002) than the control group. S. capitis colonization on nonlesional skin and anterior nares was positively associated with more severe disease in rural (48.310.8 vs. 39.711.5, P = 0.045) and urban cases (74.9 +/- 10.3 vs. 38.4 +/- 13, P = 0.004), respectively. Biofilm formation was similar between cases and controls, independent of rural-urban living. Conclusion CoNS colonization is associated with AD and disease severity and may be implicated in AD exacerbations. Studies are needed to understand their underlying pathological contribution in AD pathogenesis.